Generally, when a vehicle is driven, combustion noise is generated in an engine compartment of the vehicle and may flow into the interior of the vehicle. Such combustion noise may be generated and propagate into the interior of the vehicle at various magnitudes depending on such factors as the opening angles of engine valves associated with an engine rotation speed, the position of the accelerator pedal, the number of passengers, and various temperature conditions of the interior of the vehicle.
The combustion noise may be generated as a low frequency combustion noise or a high frequency combustion noise depending on the driving condition of the vehicle. Low frequency combustion noise may be reduced by calculating a phase of the low frequency combustion noise and then outputting a reverse-phase sound through a speaker installed in the interior of the vehicle.
However, it is difficult to effectively reduce high frequency combustion noise generated in the engine compartment of the vehicle. As a result, while a vehicle is being driven, a driver may feel a sense of fatigue due to the high frequency combustion noise.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.